Radio-receiving apparatus



'Dec- 1942- c. J. VAN LOON 2,306,238

RADIO-RECEIVING APPARATUS Filed Feb. '7, 1959 INVENTOR. 6772,51. JPN V/R/VLOO/V BY Zw ATTORNEY.

Patented Dec. 22, 1942 RADIO -RECEIVING APPARATUS Carel Jan van Loon, Eindhoven, assignments,

signor, by mesne Netherlands, asto Radio Corporation of America, New York, N. Y., a corporation of Delaware Application February 7, 1939, Serial No. 255,005

In the Netherlands February 8, 1938 8 Claims.

The invention relates to a radio-receiving apparatus which is adapted to be automatically tuned to a plurality of pre-determined stations with the aid of a station selector consisting of a key-board, a selector disc or a similar device, and wherein the tuning members are actuated by means of a motor.

Such receiving apparatus are known per se. Thus, for example, it has been proposed to mount on the shaft by which the tuning means are actuated a switch arm which brushes along a fixed contact track of which each contact corresponds to a determined station. Upon putting the station selector into operation a voltage is applied to one of the contacts and at the same time the motor which actuates the tuning means is switched into circuit. When tuning to the desired station is attained the switch-arm passes over the contact being under tension and a circuit is closed, which results in the motor being switched out of circuit.

The tuning obtained with such a device is in general not very exact since between the moment when the motor is switched-off and the moment when the tuning means come at rest, there always elapses a certain interval of time during which the tuning means leave the desired Position. I

Fundamentally it would be possible to obtain greater accuracy by actuating the tuning means at a very slight speed owing to which the removal from the desired position during the above-mentioned lapse of time would be reduced to a small value. Such a device would, however, have thedrawback that tuning to a desired station would take too long.

The present invention has for one of its objects the provision of a radio-receiving apparatus with completely automatic tuning which adapted to be tuned very rapidly to a desired station and wherein nevertheless suflicient accuracy is obtained.

According to the invention, after the station selector has been put into operation the tuning members are initially actuated for this purpose at a high speed which is considerably reduced just before the attainment of correct tuning.

The invention will be explained more fully with reference to the accompanying drawing which represents, by bodiments thereof, and wherein Fig. 1 illus trates a modification of the invention utilizing a change speed device; Fig. 1a is a detail of a portion of the structure shown in Fig. 1; Fig. 2

is a detail of a preferred form of variable way of example, some emstanding of the invention.

Tuning is effected with the aid of a key-board having a plurality of keys or press-buttons T1, T2, T3 etc. When one of these keys is pressedin a switch is closed with the result that one contact of the fixed contact track I is connected to a conductor 2. As shown more clearly in Fig. 1a, the contact track I preferably consists of a circular disc of insulating material in which along the circumference a plurality of holes are bored. Through each of these holes passes a conductor 3 which is connected to the fixed contact of one of the switches actuated by the keys. On that side of the circular disc which is remote from the key-board the conductors 3 terminate at a plurality of contacts along which pass contacts I and II of a pair of switch arms which are mounted on the shaft by which the tuning means of the receiver are actuated. The keyboard is constructed in such manner that always only a single key can be pressed-in. If another key is pressed-in the key which has initially been pressed-in automatically snaps upwards.

The contacts I and II of the switch arms are connected to secondary windings 4 and 5 respectively of a transformer 6 whose primary winding is. connected to the terminals 1 and 8 of the alternating current mains. The ends of the windings 4 and 5 which are remote from the said contacts are connected to the conductor .2

through a conductor 9 and a coupling magnet M whose operation will hereinafter be described in detail. The actuation of the tuning means is eiiected by means of a motor connected to the alternating one of the contacts m, it

current mains via or k. For convenience,

these contacts are duplicated elsewhere in Fig. 1

in association with the means which control the contacts. Thus, contacts m are under the control of magnet M, contacts h are under the control of lever 34 and contacts .k are under control Mt which may be of discs l9 and 22, all to be described more fully hereinafter.

In the position of the various switches and contacts which is shown in Fig. 1 the receiver is suited to the reception of a signal to which the receiver has been tuned by pressing-in the key T2. The contact II of the switch-arm is located on that contact of the contact track 'l which is connected to the fixed contact of the switch actuated by the key T2 with the result that the alternating voltage set up across the winding is supplied to the coupling magnet M.

The coupling magnet M has to perform two functions. Firstly, upon excitation of the magnet M the contact m is opened and secondly the excitation of the magnet M results in that the shaft ||l becomes coupled with the shaft II, the latter being effected with the aid of a differential coupling l2 which is shown in detail in Fig. 2.

In Fig. 2 the driving shaft is denoted by II. This shaft is surrounded by a casing l3 in which run a plurality of balls H, which are in contact both with the shaft l and with the casing |3. The balls |4 run in a cage l5 which has secured to it the shaft denoted in Fig. 1 by HI. When the shaft rotates and the casing I3 is held fast, the balls r011 along the inner surface of the casing l3 and put the cage l5 into motion. The cage l5 and the shaft connected thereto turn in this case at a smaller speed of rotation than the shaft H and in the same direction.

If, on the contrary, the shaft H is turned and the casing I3 is not held fast, the balls |4 cannot roll on the inner surface of the casing. In this case the casing I3 follows the rotary movement in opposite direction but the cage i5 remains at rest.

The casing l3 may be held fast with the aid of the coupling magnet M. It the coupling magnet is not excited, the shaft secured to the cage I5 is not actuated. As soon, however, as the magnet is excited the casing 13 stops and the shaft connected to the cage l5 starts turning. In this way one obtains an extremly simple coupling which can be electrically switched on and off at will.

The coupling magnet M is so dimensioned that for retaining the casing H! a higher exciting voltage is required than for the opening of the contact 112. When the magnet M is excited by the alternating voltage set up across the secondary winding 4 the contact m is opened and, in addition, a coupling between the shafts Ill and II is brought about. If, however, the excitation of the magnet M is brought about by the lower voltage set up across the secondary winding 5, the contact m is broken, it is true,

but a coupling between the shafts l0 and II is not brought about.

When the various contacts occupy the positions shown in the figure, in which event the receiver is tuned to a signal by means of the key T2 the contact m is consequently opened but the shaft I0 is not coupled with the shaft ll.

If it is desired to tune the receiver to another station another key, for example the key T1, is pressed-in. The key T2, which was pressed-in, automatically snaps upwards and thus interrupts the circuit through which the magnet M is excited with the result that the contact m is closed and the motor Mt starts running. The

ary of gear wheels "5 and II it actuates a shaft I8 on which a disc I9 is rigidly mounted. As soon as the shaft I8 is actuated the contact is is closed in a manner which will be described later on. The disc I9 has secured to it a carrier 20 which engages an extension 2| of a disc 22 which is free to rotate on the shaft I8. The disc 22 has secured to it a carrier 23 which actuates, with the aid of a pin 24, a disc 25 mounted on a shaft 26. The latter shaft actuates a tunin condenser 21 which is consequently set in motion and this, owing to the fact that the diameter of the gear wheel I5 is considerably larger than that of the gear wheel II, at a high speed. The driving at high speed of the tuning means proceeds unaltered until the contact I of the switch arm, which moves along the contact track in the direction indicated by the arrow 28, reaches the contact of said contact track which is connected via the pressed-in key T1 to the conductor 2. At this instant the voltage set up across the secondary winding 4 is supplied to the coupling magnet M with the result that the shaft I0 becomes coupled with the shaft II and the contact m is opened. The opening of the contact m does not, however, result in the motor Mt being switched out of circuit since meanwhile the contact is has been closed.

Through the intermediary of bevel gear wheels 29 and 30the shaft l0 actuates a shaft 3| which is coupled by means of a slip coupling 32 to a shaft 33. The shaft 33 has mounted on it a lever 34 which, owing to the rotation of the shaft 33, is shifted to the right, against the action of a spring 35 and by which at the same time a bush 36 keyed to the shaft 26 is likewise moved to the right. The shaft 26 is thus displaced to such an extent that the gear wheel 31 comes into engagement with a gear wheel 38, the pin 24 getting clear of the carrier 23. The gear wheel 33 is mounted on a shaft 39 which has also mounted on it a second gear wheel 40 which meshes with a gear wheel 4| mounted on the shaft I0. Through the intermediary of the gear wheels 40 and 4| the shaft l0 consequently actuates the shaft 39 which actuates in its turn, by means of the gear wheels 31 and 38, the shaft 28 so that now, owing to the fact that the dishaft H is actuated and through the intermediameter of the gear wheel 31 is large with respect to the diameter of the gear wheel 38, the tuning means are actuated at a considerably reduced speed. At the same time when the lever 34 moves to the right the contact h is closed.

As is shown in detail in Figs. 3 and 3a, a spring 42 is laid around the shaft I8 between the discs l9 and 22, opposite ends of the spring being anchored in the respective discs. The action of the spring 42 is normally to separate the extension 2| from the carrier 20 as shown in Fig. 34. However, due to the coupling between discs 22 and 25 by way of the carrier 23 and pin 24 and the driving action of disc |9 which supports the carrier 20, the latter is forced to exert a driving force or pressure against extension 2|, as shown in Fig. 3, in opposition to the spring action of 42. As soon as the contact between the carrier 23 and the pin 24 is broken owing to the action of the lever 34, the disc 22 being loose on the shaft is turned back, due to the pressure exerted by the spring 42, over an angle of almost 360 with respect to the disc IS with the result that the extension 2| assumes the position shown in Fig. 3a. Moreover, owing to the fact that the disc 22 which carries the extension 2| turns back, the contact k is opened in a manner which will be described more fully. The opening of the contact k does not, however, result in the motor Mt being switched out of circuit since meanwhile the contact it has been closed by the action of the lever 34.

The actuation at slight speed of the. tuning means continues until the contact II of the switch arm has reached that contact of the contact track I which is connected via the key T1 to the conductor 2. At this instant the coupling magnet M has applied to it, instead of the alternating voltage of the secondary winding 4, the appreciably smaller alternating voltage of the winding 5 with the result that the coupling between the shafts l5 and If is broken whereas the contact m remains open. The shaft l5 stops so that the shaft 3| is no longer actuated. Now the lever 34 is moved to the left by the spring 35 with the result that the contact h is-opened. Now all the three contacts m, h and k are opened so that the motor is switched ofl. Due to the fact that the actuation of the shaft I5 is stopped the condenser 21 has stopped at once.

After being switched off the motor of course continues running for some time due to its inertia but it can no longer actuate the tuning means because it is effectively disconnected from the shaft. It is true that'during the movement of the lever 34 to the left the shaft 25 has also been moved to the left to such an extent that the pin 24 comes again into engagement with the carrier 23 but this engagement does not bring about at once the actuation of the shaft 25 since, due to the action of the spring 42, the carrier is on the wrong side of the extension 2| (as is shown in Fig. 3a) and consequently cannot transfer any force to said extension. To that position to the pressure of the spring 42 and to bring the carrier to the bther side of the extension 2| (as is shown in Fig. 3), which requires a complete revolution of the shaft i5. Before this revolution has been performed, the motor has stopped.

As to the construction of the switches h and k the following may be observed. .The switch It may consist of two resilient contact tongues which are pressed against one another by the lever 34 when the latter moves to the right. In its simplest construction, as shown in Fig. 3, the switch It consists of two contact tongues which are secured to the carrier 25 and the extension 2| respectively and consequently only make contact with one another when (with the arrangement shown in Fig. 3) the carrier 25 is located on the left-hand side of the extension 2| or in other words when the shafts I8 and 25 are coupled with one another. During the slow actua tion ofthe tuning means'the switch It is consequently opened. This switch is also open during the period of time in which the receiver is tuned.

to a station and this owing to the fact that the motor stops before the spring 42 has been completely stretched, i. e. before the carrier 20 is pressed again against the left-hand side of the extension 2|. When, inorder to tune the receiver to another station, one of the keys of the station selector is pressed-in, the shaft 25 is consequently not actuated at once but first the spring 42 is further stretched until the carrier 20 engages the left-hand side of the extension 2 I, at which moment at the same time the switch is is closed and the shaft 25 is set in motion.

Figs. 4 and 5 represent another embodiment of .end it is necessary first to apply a force in opof a receiving apparatus with completely automatic tuning, wherein use is made in known manner of a plurality of profiled discs S1, S2, S3, S4 (Fig. 5) which are mounted on ashaft 44 by which the tuning members (diagrammatically represented in Fig. 5 by a tuning condenser 2'!) are actuated. Such a disc is provided for each station to which the receiver can be tuned by means of the station selector.

As in the embodiment according to Fig. 1 the station selector consists of a key-board on which a key is provided for each of the stations to which the receiver can be automatically tuned. The key-board is constructed in such manner that always only a single key can be pressed-in. When another key is pressed-in, the key which has previously been pressed-in automatically snaps up.

In Fig. 4. one of the keys is denoted by T and the corresponding disc which is mounted on a shaft 44 is designated by S. The circumference of the disc S consists of a portion 45 of large diameter and of a portion 45 of smaller diameter, which portions are connected to one another by a sloping portion 41. On the circumference of the disc S runs a feeler 48 which is permanently pressed against the circumference by means of an expansion spring 45', said feeler having secured toit a lever 49 by means of which a disc 50 is turned on its shaft 5| when the feeler 48 moves up and down. The disc 55 is made of insulating material, with the exception of portions 52, 53 and 54 of the circumference which consist of conductive material. Conductors 55, 51 and 58 are connected to these points of contact 52, 53 and 54. In contact with the circumference of the disc 50 there is provided a brush 55 which, upon rotation of the disc, comes in turn into contact with the points of contact 52, 53 or 54. The brush 55 is connected via the tuning key T to a conductor 55.

For each of the stations to which the receiver can be automatically tuned there are provided corresponding conductors 55, 51, 58 and 59. A second set of such conductorsis denoted in the figure by 50. The corresponding conductors 55-59 of each of the stations are multiple or shunt-connected to four common conductors 5|, 52, 53 and 54.

Via a switch 55 whose operation will hereinafter be described more fully, the conductor 5| is connected to one of the terminals 55 of the alternating current mains. The conductors 52 and 59 are connected, each through one of the exciting windings 51 and 55 of the motor Mt, to the other terminal 59 of the mains. -The conductor 54 is connected, to the terminal 59 via the invention. These figures represent a portion a brake magnet Hi which serves to stop the tuning members after the desired tuning has been attained.

The two exciting windings 51 and 55 of the motor Mt are wound in opposite senses in such manner that upon connecting the mains to the winding 51 the motor rotates, for example in 'a' clockwise direction whereas when the mains are connected to the winding 58 an opposite direction of rotation of the motor is obtained. Those ends of the windings 51 and 58 which are connected to the conductors 52 and 53 are connected to one another through the intermediary of a condenser-1|. It is thus obtained that when the mains are connected to one of the windings an out-of-phase current is supplied to the other winding so that a rotating field is set up which puts the rotor in motion.

before the desired tuning is obtained. The manner in which this occurs will be explained more fully with reference to Fig. 5.

In Fig. 5 the stator of the motor Mt is denoted by 12 and the rotor by 13. A flywheel is mounted on the shaft 14 of the rotor. The

figure illustrates the case wherein the stator is.

not excited, in which event the rotor is pressed to the right out of the stator by a spring 16 which acts in the direction indicated by the arrow. A gear wheel 11 mounted on the shaft 14 meshes in this case with a gear wheel 18 whose diameter is large with respect to the diameter of the gear wheel 11 so that the shaft 19 on which the gear wheel 18 is mounted is driven at a low speed as long as the shaft 14 is moving.

If now the stator 12 is excited, the rotor 13 is drawn into the stator against the action of the spring with the result that the shaft 14 moves to the left to such an extent that a gear wheel 80 of large diameter, which is mounted on the shaft 14, engages a gear Wheel 8| of small diameter which is mounted on the shaft 19. In this case the shaft 19 is actuated at a high speed.

By means of a friction coupling 82 the shaft 19 is coupled with a shaft 44 on which discs S1 to S4 and tuning members 21 are mounted. The shaft 44 has mounted on it a brake disc 83 with the. aid of which, upon attainment of correct tuning, the tuning members are stopped at once owing to the excitation of a brake magnet 10.

According to the invention, the above-described construction is utilised in such manner that the excitation of the stator 12 is switched off just before the desired tuning position is attained. Owing to the mounting of the flywheel 15 on the shaft of the rotor the latter does not stop at once when the stator is switched off but continues to turn for a considerable time at an almost unreduced speed. Due to the suppression of the excitation of the stator the rotor 13 flies, however, to the right, thus bringing the gear wheels 11 and 18, instead of the gear wheels 80 and 8|, into engagement with one another with the result that the speed at which the shaft 19 is driven is considerably reduced. As soon as correct tuning is attained the brake magnet 10 is excited with the result that the tuning members are braked. Then the motor continues to run for some further time but owing to the presence of the friction coupling 82 it cannot draw the tuning members through the brake.

The manner in which the switching-off of the stator and the excitation of the brake magnet are effected will hereinafter be explained more fully with reference to Fig. 4.

In Fig. 4 the disc S is shown in the position occup'ied by this disc at the moment when the tuning members come at rest. Such is the case when the feeler 48 is just in the middle of the sloping portion 41 owing to the fact that at this moment the disc 50 occupies a position such that the brush 55 makes contact with the point of contact 54 so that via 66, 65, 6|, 59, T, 55, 54. 51, 64, 10 and 69 a circuit is closed and consequently the brake magnet 10 is excited with the result that the tuning members and the discs S1-S4 immediately stop. The point of contact 54 15 made as narrow as possible in order to ensure very correct tuning. The minimum width of the point of contact 54 is determined by the time which elapses between the moment when the abovementioned circuit is closed and the moment when the tuning members come at rest, and by the speed of revolution of the disc 50. The lower the speed of revolution of the tuning members upon attainment of correct tuning, the narrower may the point of contact 54 be taken. The accuracy of tuning consequently increases as the speed of the tuning members upon attainment of correct tuning is decreased.

If it is desired to tune the receiver to another station, the key T corresponding to this station is pressed-in owing to which the key which has previously been pressed-in automatically snaps upwards and interrupts the circuit of the brake magnet 10.

At the moment When the key is pressed-in the disc S corresponding to the pressed-in key occupies an arbitrary position. The feeler 48 may consequently be on the portion of large diameter or on the portion of small diameter 46 or on the sloping portion 41 of the circumference of the disc S. If the feeler 48 is on the portion 45 of the circumference of the disc S, the disc will have turned clockwise to such an extent that the brush makes contact with the point of contact 53. In this case, upon pressing-in the key T, a circuit 66, 65, 6!, 59, T, 55, 53, 58, 62, 61, 69 is closed so that the exciting winding 61 of the motor Mt is connected to the mains. The motor starts running and this in clockwise direction. Owing to the excitation of the winding 61 the rotor 13 (Fig. 5) is drawn into the stator with the result that the gear wheels and 8| are caused to mesh with one another. The tuning members consequently turn at a high speed, and this in counter-clockwise direction so that the feeler 48 moves with respect to the disc S towards the sloping portion 41.

If, on the contrary, upon pushing-in the key T, the feeler 48 is in contact with the portion of small diameter 46 of the circumference of the disc S the disc 50 occupies a position such that the brush 55 makes contact with the point of contact 52. Upon pressing-in the key T the winding 68 of the motor Mt is connected in this case to the mains with the result that the motor rotates in opposite direction. Again in this case the feeler 48 moves with respect to the disc S towards the sloping portion 41.

In both cases the actuation at high speed of the tuning member continues until the feeler 48 reaches the sloping portion 41 of the circumference of the disc S. At this instant the-disc 50 starts rotating and after a short time it interrupts the motor circuit owing to the fact that the brush 55 leaves the point of contact 52 or 53 and reaches an insulated portion of the circumference of the disc 50, which results in that the motor is switched off and the speed at which the tuning members are actuated is considerably reduced in the above-described manner. The tuning members continue to rotate at a low speed, the feeler passing meanwhile over the sloping portion 41 of the circumference of the disc S. As soon as the feeler has reached the middle of this sloping portion the disc 50 has taken a position such that the brush 55 makes contact with the point of contact 54 with the result that the brake magnet 10 is excited and the tuning members are braked.

V able devices each thereof A complication occurs if two stations having a slight difference in frequency are selected the one after the other by means of the station selector. For in this case it may occur that, upon pressing-in the key T, the feeler 4| is already on the sloping portion 41 of the circumference of the disc 8 so that upon pressing-in the key the motorv circuit would not be closed. In order to prevent this there has been provided a switch 05 with the aid of which one of the motor windings can be directly connected to the mains.

After the switch 65 has been shifted different cases may occur. At this instant one of the points of contact 52 or 53 make contact with the brush 5! so that either the motor continues to rotate in the same direction or reverses its direction of rotation and then causes the tuning members in the above-described manner to occupy the desired position.

It may also occur that after the switch 85 has been shifted the feeler 48 is on the sloping por-' tion 41 of the circumference of the disc 8 so that by shifting the switch 65 the motor circuit is interrupted. Owing to the presence of the flywheel the motor still continues to run for some time, thus actuating the tuning members at a low of the disc 50 will in generalvariablespeed transmission means connected between the motor and the adjustable shaft, a source of energizing current for the motor, a plurality of motor circuits adapted to be connected between the motor and the source of current, one

of said circuits acting upon connection thereof to effect the operation of the motor in one direction, the other of said circuits acting upon connection thereof to effect the operation of the motor in the opposite direction, an operable main switch, a multi-position selectively operable switching means arranged so that with the main switch closed the motor isconnected to the source switching means, said motor being arranged so speed. If upon shifting the switch 85 the 'desired position of the tuning members had not yet been attained, this actuation continues until the brush 55 makes contact with the point of contact 4 of the disc 50, at which instant the tuning members are braked. If, on the contrary, when the switch I had been shifted, the tuning members had already passed the desired position the motor continues to run until the brush it comes into contact with any of the points of contact 62 and I3 and then reverses its sense of rotation and brings the tuning members into the desired position from the other direction.

' The transmission shown in Fig. 5 wherein the motion of the motor shaft is transmitted by means of gear wheels to the shaft of the tuning condensers, has the drawback that at the moment when the gear wheels come into engagement with one another they have different peripheral speeds, which may give rise to an annoying cracking noise upon changing-over and to a rapid tear and wear of the gear wheels. This drawback may be removed by utilising friction couplings instead of gear wheels.

What I claim:

1. In a control shaft positioning means including a plurality of selectively operable devices each acting upon selective operation to position the shaft to any one of a plurality of difl'erent posi tions, a reversible electric motor, variable speed transmission means the control shaft, a plurality of operable switching means associated with said selectively operhaving positions for operating the motor in a forward and reverse difor connecting the motor to as to control the variable speed transmission means in such a way that a lowtransmission ratio of coupling between the motor and the adjustable shaft is provided when the motor is in a de-energized condition whereas a high transmission ratio is provided when the motor is energized, said motor being arranged so that in the operation thereof sufficient momentum is provided to maintain the motor in operationfor an appreciable length of time after the motor is rection, and, a ne tral siti f t w u Do on or S oppmg able means for controlling the operation of the motor, means connected for operation with said control shaft for operating said switching means, means acting in response to operating potential applied to the motor for adjusting the variable speed transmission means so as to provide a high speed driving connection'between the motor and the control shaft, and means for adjusting the variable speed transmission means toprovide a low speed driving connection between the motor and the control shaft upon removal of the motor operating potential. I

2. In a shaft positioning system, an adjustable shaft, a reversible motor for driving said shaft,

lie-energized.

3. The arrangement described in claim 2 in combination with operable means for braking the motor, said means becoming operative to stop the motor when said main switch is closed and the selectively operable switching means assumes said intermediate position.

4. The arrangement described in claim 2 char-' acterized by that the motor is of. the type wherein the armature is shifted upon an energizing potential being applied to the motor andby that means are provided for operating the variable speed transmission means in accordance with the position of the motor armature.'

5. In a control system, a control shaft, an electric motor for driving said shaft, multi-step transmission means coupling the motor to the control shaft, said motor having a movable element acting in response to operating potential applied to the motor for adjusting the change speed means to provide a driving connection between the motor and the controlshaft through one of the steps of said transmission means, and means acting upon removal of the motor operating potential for adjusting the change speed means to. provide a driving connection between the motor and the control shaft through another one of said transmission steps.

6. In the arrangement described in the next preceding claim, a plurality of selectively opermo'tor, each of said selectively operable means representing a desired position of said control tion of which is controlled by means of a plurality of selectively operable devices each acting upon selective operation thereof to effect through operation of the motor the adjustment of the control shaft to any one of a plurality of positions by applying an operating potential to the motor to thereby start the motor running and removing the operating potential when the control shaft has been brought to a position which is near that represented by the operated selectively operable device,- said positioning system being arranged to have suflicient momentum once it is set in motion to drive the control shaft an appreciable distance beyond the point of cut-off of the motor operating potential, variable speed ,15

transmission means coupling the motor to the control shaft, means acting in response to operating potential applied to the motor for adjusting the variable speed transmission means so as to provide a high speed driving connection between the motor and the control shaft, means for adjusting the variable speed transmission means to provide a low speed driving connection between the motor and the control shaft upon cut of! of the motor operating potential, and means for braking the motor when the control shaft reaches the desired position.

8. In a control system, a control shaft, 9. source of current, a reversible motor for driving said shaft, variable speed transmission means coupling the motor to the control shaft, means acting in response to operating potential applied to the motor for adjusting the variable speed transmission means so as to provide a high speed driving connection between the motor and the contrcl shaft, means for adjusting the variable speed transmission means to provide a low speed driving connection between the motor and the control shaft upon cut off of the motor operating potential, means for braking the motor when the control shaft reaches the desired position, a plurality of reversing switches for the motor, each of said reversing switches having positions for operating the motor in a forward and a reverse direction and a range of neutral positions of appreciable extent intermediate said forward and reverse positions for stopping the motor, a plurality of selectively operable switches one for each of said reversing switches, each of said selectively operable switches being in circuit with its reversing switch and the motor and acting upon operation to connect the motor to the source when said reversing switch is in an operating position, operating means for the reversing switches connected with the control shaft and arranged so that operation of one of said selectively operable devices effects the movement of its associated reversing switch to a position which is within said neutral range of positions in response to movement of said control shaft, and an auxiliary switching means for providing a direct connection between said motor and said source of current to thereby assure energization of the motor in the event that the reversing switch of an operated selectively operable device is within said neutral range of positions and for breaking said direct connection between the motor and the source of current after said motor has operated for a predetermined interval of time.

CAREL JAN VAN LOON. 

